Depolarization triggers intracellular magnesium surge in cultured dorsal root ganglion neurons.
Intracellular magnesium concentration ([Mg2+]i) of cultured dorsal root ganglion (DRG) neurons was measured using the magnesium indicator Mag-Fura-2/AM. [Mg2+]i was 0.48 +/- 0.08 mM (mean +/- SEM, n = 23) at rest, and it increased 3-fold by depolarization with a 60-mM K+ solution. The [Mg2+]i increase was observed in the absence of extracellular Mg2+, but the increase disappeared in the absence of extracellular Ca2+. 50 microM cadmium or 100 microM verapamil, a Ca2+ channel blocker, also diminished the rise of [Mg2+]i. The additional measurement of an intracellular Ca2+ concentration ([Ca2+]i) indicated that the [Mg2+]i rise requires a threshold concentration of [Ca2+]i to be reached; above 60 nM. The present results indicate that depolarization induces a Ca2+-influx through voltage dependent Ca channels and this causes the release of Mg2+ from intracellular stores into the cytoplasm.
Kato
H
H
Department of Bioengineering, Faculty of Engineering, Soka University, Tokyo, Japan. hideki@t.soka.ac.jp
Gotoh
H
H
Kajikawa
M
M
Suto
K
K
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects*; D002478:Cells, Cultured; D004558:Electric Stimulation; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008274:Magnesium / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D005456:Fluorescent Dyes; D002104:Cadmium; C058776:2-(2-(5-carboxy)oxazole)-5-hydroxy-6-aminobenzofuran-N,N,O-triacetic acid; D014700:Verapamil; D008274:Magnesium; D002118:Calcium; D016257:Fura-2